Straightforward electrochemical synthesis of a CoO nanopetal/ZnO nanoplate p-n junction for photoelectrochemical water splitting.

Hydrogen production through photoelectrochemical (PEC) reactions is an innovative and promising approach to producing clean energy. The PEC working electrode of a CoO/ZnO-based p-n heterojunction was prepared by a straightforward electrochemical deposition with different deposition times onto an FTO (Fluorine-doped Tin Oxide) glass substrate. The successful synthesis of the materials was confirmed through analysis using XRD, FTIR, SEM-EDX, DRS, and PL techniques. Mott-Schottky plots and some characterization studies also checked the determination of the formation of the p-n junction. CoO/ZnO/FTO with a CoO deposition time of 2 minutes exhibited the lowest onset potential of 0.82 V and the lowest overpotential of 470 mV at a current density of 10 mA cm . Furthermore, the photo-conversion efficiency of the CoO/ZnO/FTO sample showed 1.4 times higher current density than the ZnO/FTO sample. A mechanism is also proposed to enhance the CoO/ZnO/FTO electrode photo-electrocatalytic activity involved in the water-splitting reaction. The CoO/ZnO/FTO electrode shows significant potential as a promising PEC electrode to produce hydrogen.